The observation by Okazaki of the transient accumulation of pulse-labeled DNA fragments in bacteria has lead to the model of discontinuous DNA replication. Recent studies by Tye et al. (1977) have shown that uracil incorporation into nascent DNA can result in the transient accumulation of Okazaki fragments. Crucial to the identification of true discontinuous replicative intermediates is an investigation of the origin(s) of Okazaki fragments. This require an understanding of (1) the properties of DNA fragments that arise from uracil excision repair, (2) other mechanism(s) for post-replication repair using uracil excision repair as a starting point, (3) the possible function(s) of uracil incorporation in DNA. The information would enable one to distinguish between DNA fragments that arise from post-replication repair and true intermediates that result from discontinuous DNA replication.